The present invention relates to a cutting insert, in particular for milling camshafts, with at least one cutting edge composed of several sections. Such cutting inserts have been known in principle for a long time.
The manufacture of camshafts is usually done conventionally in that a camshaft is firstly cast in a mould, wherein the cast camshaft nevertheless does not yet possess sufficient accuracy in its dimensions for it to be used as a camshaft. The camshaft thus manufactured, cast with excess dimensions, is therefore subjected to further stages of finishing. Parts of the camshaft, in particular journals thereof, have an exact circular or cylindrical shape, and a common axis. These parts are as a rule worked or manufactured on a suitable lathe by turning. The cam contours are subsequently milled with so-called disc milling cutters about the periphery of which a large number of cutting inserts are arranged, the combined cutting edge profile of which corresponds in its entirety to the cross-section profile of a cam, wherein the disc milling cutter is advanced to the corresponding cam and the camshaft then completes a 360° rotation, wherein according to the path of the cam, the gap between the milling cutter axis and the axis of the camshaft is varied so that overall the desired cam contour is produced in a cutting plane perpendicular to the axis of the camshaft. The contour of the cam in a cutting plane that includes the axis of the camshaft is determined by the contour of the cutting edges on the disc milling cutter. The cylindrical coaxial sections of the camshaft remain unworked or are subsequently finished by grinding. Thus, after casting the camshaft, a total of at least three different stages of working, on three different machines, and corresponding loading of machines is necessary to manufacture a camshaft in the conventional manner.
A method has recently been developed by means of which the procedure of rotating of cylindrical, concentric sections is omitted, and instead these cylindrical sections are also manufactured with the aid of disc milling cutters, the cutting inserts of which are configured and arranged such that they shape parts of the contour of these cylindrical sections as well as the end faces of the cams, again seen in a formation that includes the axis of the camshaft. In this way, parts of the cylindrical sections as well as the cam contours of the camshaft can be manufactured in a single loading on the same milling machine. The remaining parts of the cylindrical sections are exclusively ground or remain raw and unworked.
As the cams extend further out radially than the cylindrical sections of the camshaft, for accurate finishing of the cylindrical sections by grinding, undercuts must be manufactured in the corner areas in the transition between the cylindrical section and an adjacent cam, that is to say small groove-like indentations in the corner areas, so that the cylindrical sections can be manufactured in an accurately defined manner. With this working procedure, the end faces of the cams must additionally be manufactured or worked, which is conventionally done by turning. On the other hand, with this milling procedure, the cylindrical surfaces themselves do not necessarily have to be manufactured as they have only a small over-measurement, and can also be fabricated directly by grinding. Consequently, the cutting inserts for flat milling of the cam end faces as well as the manufacture of undercuts on the cylindrical coaxial surfaces of the camshaft have to have a completely different contour and have a different cutting edge path than for manufacturing the cam contour. Thus, at first glance it is necessary to equip the different milling cutters used on the one hand for manufacturing the undercuts in the corners areas of the cylindrical sections, and the end faces of the cams, with different cutting inserts than the milling cutters that manufacture the cam contour. As these milling cutters are disc milling cutters with a relatively large diameter, along the periphery of which as large a number as possible of cutting inserts is arranged in order to obtain as long an uninterrupted operating time as possible with one disc milling cutter, this obviously means a very high consumption of cutting inserts when the cutting edges of the inserts of a milling cutter are worn out.
With respect to this prior art, the object of the present invention is to provide a cutting insert, the use of which will allow considerable savings to be obtained.